N,N'-[(thiocarbonyl)thio]dimorpholine is a rubber accelerator which has good scorch protection and provides a fast rate of cure. Unfortunately, the compound is not stable on storage alone at ambient temperatures, as evidenced by its loss of accelerator activity with time. In fact, at temperatures of 110.degree.-115.degree. F., commonly encountered in warehouses during the warm months, the compound suffers considerable loss of activity in a relatively short time. If a means for stabilizing this accelerator could be found, a long-felt need would therefore be satisfied.